BOURNS SinglFuse SMD Fuses User Guide
- July 26, 2024
- BOURNS
Table of Contents
- SINGLFUSE SMD FUSE PRODUCT LINE CHART
- NORMAL OPERATING CURRENT AND RATED CURRENT
- RATED VOLTAGE AND APPLICATION VOLTAGE
- AMBIENT TEMPERATURE AND TEMPERATURE DERATING
- MELTING INTEGRAL (I2 t) AND INRUSH CURRENT
- FUSING CHARACTERISTICS AND TIME-CURRENT CURVE
- PARAMETRIC SEARCH TOOL
- Instruction
- References
- Read User Manual Online (PDF format)
- Download This Manual (PDF format)
BOURNS SinglFuse SMD Fuses User Guide
A properly selected fuse is widely regarded as the most effective way to safeguard a circuit against potentially catastrophic short circuit events. To this end, Bourns® SinglFuse™ SMD Fuses represent a robust and reliable solution that provides effective overcurrent protection to circuits. These fuses are available in a range of standard SMD packages that accommodate a variety of application needs, with sizes spanning from 0402 to 3812. The fuses are engineered using seven distinct technologies that incorporate board voltage and current ratings, operating temperature ranges, and fusing characteristics, making them an attractive option for designers seeking a versatile and customizable solution. A comprehensive overview of Bourns® SinglFuse™ SMD Fuses portfolio is outlined in the SinglFuse™ SMD Fuse Product Line Chart below. To facilitate the selection of the most appropriate fuse from this range, this article presents key considerations to guide the selection process. To enhance the value of these considerations, a practical example is presented to illustrate their application in real-world scenarios.
SINGLFUSE SMD FUSE PRODUCT LINE CHART
*Meets Bourns’ internal AEC-Q200 equivalent test plan.
When selecting a SinglFuse™ SMD Fuse, several factors must be considered, including the normal operating current in the circuit, the maximum operating voltage (AC or DC) in the circuit, the ambient temperature during normal operation, the overload current and fusing time required for the fuse to open, the maximum interrupting current, surge currents, inrush currents, and start- up currents, physical dimension limitations, and safety agency approvals such as UL, CSA, TÜV, or PSE.
NORMAL OPERATING CURRENT AND RATED CURRENT
Fuses are devices that are sensitive to temperature, and their ratings for current, voltage, and interrupting capability are commonly tested under ambient temperature conditions of 25 °C. In order to prevent nuisance tripping, it is recommended that fuses be operated at a maximum of 75 % of their rated current under these conditions.
For instance, SF-0603SP200R-2 is rated at 2 A at 25 °C, and it is advised not to exceed an operating current of 1.5A.
Electrical Characteristics
Model| Rated Current (A)| Resistance (Ω) Typ. 1| Rated
Voltage 1| Interrupting Rating| Typical I 2t (A2s)2| Agency
Recognition
---|---|---|---|---|---|---
cUL: E198545
SF-0603SP100R-2| 1.0| 0.115| 63 VDC| 50 A @ 63 VDC| 0.059| ✓
SF-0603SP150R-2| 1.5| 0.059| 0.13| ✓
SF-0603SP200R-2| 2.0| 0.033| 0.21| ✓
SF-0603SP300R-2| 3.0| 0.0159| 0.71| ✓
SF-0603SP400R-2| 4.0| 0.01| 0.96| ✓
SF-0603SP500R-2| 5.0| 0.00677| 2.05| ✓
SF-0603SP600R-2| 6.0| 0.0063| 3.47| ✓
SF-0603SP700R-2| 7.0| 0.0047| 5.04| ✓
SF-0603SP800R-2| 8.0| 0.0043| 6.5| ✓
Notes:
- Resistance value measured with ≤10 % rated current at 25 °C ambient. Tolerance ±25 %.
- Melting I2t calculated at 0.001 second pre-arcing time
RATED VOLTAGE AND APPLICATION VOLTAGE
The rated voltage of a fuse is the maximum voltage at which it can safely
interrupt a short circuit current within its rated current.
It must be greater than the maximum operating voltage of the circuit.
Therefore, the SF-0603SP200R-2 fuse, with a rated voltage of 63 VDC, can be
utilized in circuits where the maximum operating voltage is below 63 VDC.
Model| Rated Current (A)| Resistance (Ω) Typ. 1| Rated
Voltage 1| Interrupting Rating| Typical I 2t (A2s)2| Agency
Recognition
---|---|---|---|---|---|---
cUL: E198545
SF-0603SP100R-2| 1.0| 0.115| 63 VDC| 50 A @ 63 VDC| 0.059| ✓
SF-0603SP150R-2| 1.5| 0.059| 0.13| ✓
SF-0603SP200R-2| 2.0| 0.033| 0.21| ✓
SF-0603SP300R-2| 3.0| 0.0159| 0.71| ✓
SF-0603SP400R-2| 4.0| 0.01| 0.96| ✓
SF-0603SP500R-2| 5.0| 0.00677| 2.05| ✓
SF-0603SP600R-2| 6.0| 0.0063| 3.47| ✓
SF-0603SP700R-2| 7.0| 0.0047| 5.04| ✓
SF-0603SP800R-2| 8.0| 0.0043| 6.5| ✓
AMBIENT TEMPERATURE AND TEMPERATURE DERATING
The current carrying capability of a fuse is determined by its performance
during testing conducted at a specific ambient temperature of 25 °C. However,
the operating life of a fuse is known to be significantly affected by changes
in ambient temperature. As temperature increases, a fuse’s operating life is
reduced, making the derating curve an essential consideration when selecting a
fuse.
To compare the derating curves of five SinglFuse™ SMD Fuses, please refer to
Figure 1.
Figure 1 – Temperature derating curves of SinglFuse™ SMD Fuses
MELTING INTEGRAL (I2 t) AND INRUSH CURRENT
Melting Integral (I2 t) and Inrush Current is influenced by various factors such as construction, material, pattern design and crosssectional area. Bourns SinglFuse™ SMD Fuses incorporate seven distinct technologies, each featuring a unique construction and corresponding I2 t value. As an illustration, SF- 0603SPA200R-2 exhibits a typical I2 t value of 0.21 (at 1 ms pre-arcing time) as specified in the datasheet.
Model| Rated Current (A)| Resistance (Ω) Typ. 1| Rated
Voltage 1| Interrupting Rating| Typical I 2t (A2s)2| Agency
Recognition
---|---|---|---|---|---|---
cUL: E198545
SF-0603SP100R-2| 1.0| 0.115| 63 VDC| 50 A @ 63 VDC| 0.059| ✓
SF-0603SP150R-2| 1.5| 0.059| 0.13| ✓
SF-0603SP200R-2| 2.0| 0.033| 0.21| ✓
SF-0603SP300R-2| 3.0| 0.0159| 0.71| ✓
SF-0603SP400R-2| 4.0| 0.01| 0.96| ✓
SF-0603SP500R-2| 5.0| 0.00677| 2.05| ✓
SF-0603SP600R-2| 6.0| 0.0063| 3.47| ✓
SF-0603SP700R-2| 7.0| 0.0047| 5.04| ✓
SF-0603SP800R-2| 8.0| 0.0043| 6.5| ✓
When an overcurrent event occurs, it generates thermal energy. If the duration of this event is brief, it can be likened to an inrush current, and the energy produced can be estimated by the area of the waveform displayed in Figure 2.
Figure 2 – Inrush waveforms and I2 t calculations
To prevent premature failure of a fuse element, it is important to consider
the effect of inrush current even when it does not cause melting of the fuse.
In order to select a fuse with appropriate inrush withstand capability, it is
necessary to calculate the circuit’s inrush energy and compare it with the
melting time and I 2 t curve of the fuse.
The fuse’s melting I2 t value must be equal to or greater than the product of
the inrush I2 t and a fuse derating factor (as shown in Figure 3) to ensure
proper sizing and to avoid early failure.
Figure 3 – I2 t derating vs. inrush current withstanding number
FUSING CHARACTERISTICS AND TIME-CURRENT CURVE
The DC time-current characteristic of a fuse depicts the relationship between its pre-arcing time and the current flowing through it. This characteristic is instrumental in selecting a fuse with the desired fusing time, as fuses with the same current rating can have different time-current characteristics.
In the case of SF-0603SP200R-2, which falls under the category of 1 second to
120 seconds fusing characteristics, applying 4 A current would result in an
average pre-arcing time of approximately 3.5 seconds.
Product Selection Guide Bourns® SinglFuse™ SMD Fuses FUSING CHARACTERISTICS
AND TIME-CURRENT CURVE SF-0603SP-R S
Clearing Time Characteristics for Series
| % of Current Rating | Clearing Time at 25 °C |
|---|---|
| Min. | Max. |
| 100 % | 4 hours |
| 200 % | 1 second |
Average Pre-Arcing Time vs. Current Curves
PARAMETRIC SEARCH TOOL
The Parametric Search tool available online simplifies the selection process.
To access more details about these products, please refer to the Bourns®
SinglFuse™ SMD Fuse Technical Library
PRACTICAL EXAMPLE:
When the inrush is present, follow Step A to B to C When the inrush is negligible or absent, follow Step A to C
Instruction
References
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